Hold current and trip behaviour
The 1206L050YR is a Littelfuse POLY-FUSE® series polymeric PTC resettable fuse. It holds 500 mA continuous without tripping; when the fault current pushes the internal temperature past the polymer's switching threshold, the resistance jumps from a 150 mOhm minimum to a 700 mOhm maximum post-trip state, limiting the current to a safe level. The trip time is 100 ms at the fault current — fast enough to protect a 6V rail feeding a USB port or a sensor node before the downstream regulator overheats. After the fault clears and power cycles, the PTC resets and the circuit returns to normal operation.
Fault current ceiling and voltage limit
Rated for a maximum fault current of 100 A at 6V. The 6V maximum voltage restricts this part to low-voltage DC rails — USB VBUS (5V), battery-powered handhelds, or logic supplies. Do not use it on 12V or 24V industrial buses; the voltage exceeds the PTC's dielectric withstand and the device may not trip cleanly.
Package and board integration
The concave termination profile improves solder-joint inspection — the side-wall fillet is visible after reflow, unlike a flat-chip termination where the joint hides under the body. Surface-mount mounting per standard 1206 footprint. The Tape & Reel packaging (Cut Tape option available) feeds into pick-and-place without a feeder change. Store the reels in a dry cabinet if the ambient humidity exceeds 60% RH — the moisture sensitivity level is not stated, but a 24-hour bake at 125°C before reflow is a safe precaution for any 1206 polymeric device.
Temperature range and approvals
The -40°C low end means the PTC trips at a slightly higher current in cold environments, but the trip time remains within the 100 ms window. Carries cURus and TUV approvals — the cURus mark certifies compliance with UL 1434 and CSA C22.2 No. 0.4 for polymeric PTCs; TUV certification confirms it meets IEC 60738-1 for thermally sensitive resistors. Both are required for equipment sold into North American and European markets.